resposta: alternativa E
Resolução:
$\,C_{n,k}\,={\Large\binom{n}{k}}\,=\,\dfrac{n!}{k!(n-k)!}\,=\,$$\,=\dfrac{7!}{4!3!}\,=\,\dfrac{5\centerdot 6\centerdot 7}{6}\,=\,35\,$

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